Room temperature molding of amorphous dielectrics via van der Waals anisotropy at the nanoscale.

Abstract

Mechanical instabilities produce periodic out-of-plane deformations, but applications remain limited by the need for elastic substrates and weak controllability. Here, we induce coherent, instability-driven buckling in both van der Waals (vdW) layers and underlying amorphous silica at room temperature, achieving precise spatial control and deterministic orientation. Electron-beam builds crystal-axis-dependent stress in α-MoO₃, while simultaneously facilitating viscous flow in silica, producing sinusoidal wrinkles at subwavelength whose dimension are tunable by α-MoO₃ thickness and electron dose. These wrinkles diffract light as on-chip optical gratings. We show coherent buckling across vdW heterostructures and peel off α-MoO₃ post-buckling, leaving imprinted silica. Similar crystal-aligned wrinkles appear on amorphous Al₂O₃ and SiN_x. By removing reliance on elastic substrates, this work extends the scope of instability-driven, lithography-free subwavelength patterning to CMOS-relevant dielectrics.